Field
This disclosure relates generally to semiconductor processing, and more specifically, to a bonded wafer structure having cavities with low pressure.
Related Art
During wafer bonding, two wafers are typically stacked and aligned prior to bonding the wafer pair. In order to efficiently outgas the wafers, the wafers are separated by removable spacers, such as with metal tabs which are part of the wafer handling equipment (e.g. pivoting metal tabs of a wafer chuck). After the outgassing, the wafers are brought together during wafer bond in which the removable spacers are removed. However, the wafers frequently slip or move when the removable spacers are removed, thus compromising the alignment of wafers. This is especially problematic when bonding seals on each wafer must be aligned to create appropriate vacuum or low pressure cavities, such as for micro-electro-mechanical system (MEMS) devices. If the wafers slip and misalign during removal of the removable spacers, the appropriate low level of pressure cannot be maintained in the cavities which may result in reduced device performance or reduced device longevity. Therefore, a need exists for improved wafer bonding which allows for wafer separation during outgassing without resulting in misalignment during bonding.